Summary In the early morning hours of 03February2001, while en route to the Sable Gas Fields off Sable Island, fire erupted in the starboard engine room of the ThebaudSea. The engine room was quickly sealed after the crew mustered. With the crew accounted for, CO2 was released into the space. Approximately two and one-half hours later, after determining that the fire had been extinguished, a damage control team, equipped with hand-held fire extinguishers and fire hoses, entered the starboard engine room. Isolated pockets of fire were extinguished, hot spots cooled and the fire declared out. Several hours later, the crew was able to re-establish auxiliary and propulsion power in the port engine room. The vessel then returned to Halifax, Nova Scotia, under escort. Ce rapport est galement disponible en franais. Factual Information Particulars of the Vessel Description of the Vessel The ThebaudSea is an offshore platform supply and diving support vessel of welded steel construction. The superstructure, which houses the wheelhouse, accommodation and the port and starboard engine rooms, is located forward. Each engine room contains three diesel-electric generators (main engines). A moonpool is located just aft of the superstructure and the dry bulk and liquid mud tanks are situated just aft of the moonpool. The port and starboard motor rooms are located aft. The vessel is equipped with a dual redundant dive-capable dynamic positioning system and carries an unmanned machinery space (UMS) certification. History of the Voyage The ThebaudSea departed the Mobil dock at Dartmouth, Nova Scotia for the Sable gas fields on 02February2001 at 2010.2 Until the time of the occurrence, the voyage was uneventful. Winds were from the northeast at 20knots, 1to 1.5m seas and an air temperature of 0Celsius (C). Shortly before 0400, the third engineer, after completing rounds of the port and starboard engine rooms, proceeded to the mess for a coffee. At 0400, a machinery alarm system sounded and the third engineer proceeded towards the control room to determine the cause of the alarm. When he opened the starboard engine room door, he saw flames emanating through the open steel grating at the mezzanine level. He immediately closed the door, proceeded back to the change room and activated the fire alarm. He telephoned the wheelhouse and informed the second officer of the fire. The second officer activated the general alarm and broadcast fire in the engine room on the internal communications system. Meanwhile, the third engineer apprised the chief engineer and the second engineer (who were resting in their cabins) of the situation while the crew mustered at their fire stations. Figure1. Plan of the engine room Shortly thereafter, the master arrived on the bridge, assumed command and sent the second officer to his muster station. The vessel's speed was reduced and the autopilot adjusted to bring her head into the wind. As the crew mustered on the afterdeck, the chief engineer proceeded to the port engine room to assess the situation and start the two remaining main generators. He transferred the starboard electrical load to the port engine room switchboard and isolated the starboard engine room switchboard. He then proceeded to his muster station and, with concurrence of the master, activated the starboard engine room fuel trip. At this time, the vessel experienced a black out. The chief engineer then proceeded to the emergency generator room where, to expedite the return of power to the vessel, he started the emergency generator and put it on load. In preparation for the release of CO2 into the starboard engine room, the master and chief engineer proceeded through a pre-release checklist and confirmed that: fuel trips were activated; ventilation fans were shut down; fire dampers were closed; the door between the port and starboard engine rooms was closed; and the watertight door between the starboard engine room and the workshop was closed remotely from the bridge. With fire activity and the temperature increasing in the starboard engine room, a decision was made to release the CO2. At 0414, with all crew accounted for, the master gave the order and the chief engineer released the CO2 into the starboard engine room. Immediately afterwards, the master contacted Sable Offshore Energy Inc. (SOEI) communication centre with the initial notification of the occurrence. According to their safety protocol, SOEI communication centre notified the appropriate authorities onshore. At 0418, the release of CO2 was confirmed by the sound of the gas in the delivery piping. Shortly after the CO2 was released, a high-pitched noise was heard coming from the monkey island. An investigation of the sound revealed blue-coloured flames estimated at six to eight metres in length issuing from the number six main generator exhaust. The master, concerned with the possibility of fire in the engine exhaust trunking, ordered the standby fire team to rig fire hoses and prepare for possible boundary cooling; however, cooling was not required. Numerous updates were sent to the SOEI communications centre and, at 0428, the vessel was informed that Search and Rescue (SAR) resources had been tasked to render assistance. After the release of the CO2, smoke and combustion gases were observed escaping from the engine room ventilation exhaust, indicating the seal to the compartment had been breached. The starboard engine room boundaries were monitored and, at 0500, it was decided to attempt a visual observation of the starboard engine room through the after watertight door. Control of the watertight door was switched to local control and the door was cracked open. The fire team reported an in-draft air transfer and, under orders from the master, the door was closed. Ten minutes later, a second visual observation was made and, once again, the door was opened slightly. This time, the fire team reported an outdraft air transfer. The door was opened further to approximately 30centimetres but, as visibility was zero, the door was closed once again. The fire team withdrew to the afterdeck. The chief engineer, who was in communication with the bridge, informed the team that entry into, and reconnaissance of the starboard engine room was critical. At 0533, the fire team leader, wearing self-contained breathing apparatus (SCBA) and carrying a handheld fire extinguisher, made the first entry into the starboard engine room. The fire team leader reported flames inboard of the number four main generator and discharged a dry chemical extinguisher at the fire. He then proceeded to the mezzanine level, emptied his extinguisher into observed flames in the area, and retreated to the workshop. Seventeen minutes later, a fire team of two made a second entry into the starboard engine room and proceeded back to the mezzanine level. They extinguished any observed flames with dry chemical extinguishers. The fire team proceeded back to the lower level of the starboard engine room and discharged their extinguishers at an observed hot spot. Detecting no other sign of flame, they retreated to the workshop. At 0621, the fire team made a third entry in the starboard engine room with fire hoses and spray nozzles to cool off any hot spots. The mezzanine level was inspected first, followed by the lower level. The fire team continued to spray the area as they backed out of the engine room to renew their air bottles. Twenty-two minutes later, a fourth entry was made into the starboard engine room to further quell any hot spots. The fire was confirmed extinguished at this time. At 0723, the first SAR resource, HMCSSt.John's, which had been tasked by the Joint Rescue Co-ordination Centre (JRCC) - Halifax, arrived on scene and a military team boarded the ThebaudSea to offer assistance. At 0848, a fire team consisting of vessel and military personnel entered the starboard engine room with heat-detecting thermal-imaging and air quality assessment equipment. They reported that the fire was out, there were no hot spots and the atmosphere was clean. With the starboard engine room reconnaissance completed, the fire team left the engine room and the vessel commenced to ventilate and expel the remaining smoke. At 0925, the engineering department started up the three main generators in the port engine room. Control of the port propulsion system, as well as a bow thruster and steering gear, were re-established. With all the necessary checks and trials completed, the military team departed the vessel and HMCSSt.John's was released by JRCC - Halifax. At 1115, the ThebaudSea, escorted by CCGCSambro and the VentureSea, got underway and, upon arrival at Halifax, secured alongside the Mobil Dock at 2130. Boat and Fire Drills While regulations require boat and fire drills to be conducted at intervals not exceeding one month,3 the company's safety handbook called for all vessels engaged in offshore activities to carry out the drills on a weekly basis. Search and Rescue Operations Concurrent with the release of the CO2, a call was made to the SOEI communication centre, informing of the vessel's situation. SOEI relayed the information to JRCC - Halifax who immediately tasked a SAR helicopter, a Hercules aircraft, a naval destroyer and two Canadian Coast Guard SAR cutters to render assistance. While both aircraft were preparing for take-off, the vessel reported the fire under control and the aircraft were stood down. Upon arrival on-scene, HMCSSt.John's offered the services of a full firefighting team equipped with air quality meter and an infrared thermographic device to the ThebaudSea. As the fire was now under control, the master of the ThebaudSea elected to use the military personnel and their equipment to advantage to assist the ship's complement in exploring and assessing the starboard engine room. The compatibility of the SCBA between the vessels permitted uninterrupted use of the equipment to combat fire. At 0910, the CCGCBickerton, CCGCSambro and the VentureSea arrived on scene. As their direct assistance was not required, both cutters were asked to stand by. Damage to the Vessel Fire damage to the forward section of the starboard engine room and mezzanine level was extensive. Most of the electrical cables were either heavily damaged or destroyed. The steel deck grating directly above the No.4 main generator was noticeably distorted. Fire damaged the paint work on the mezzanine level directly above the No.4 main generator. Heat from the fire caused the paint on the bulkhead separating the port and starboard mezzanines to blacken and blister in the port engine room. Fire damage to the No.4 main generator was primarily to the forward section of the generator, namely: primary and secondary fuel oil filters; freshwater header tank; vibration damper; various accessories; and wiring harnesses mounted on the generator. Vessel/ Crew Certification and Personnel Experience The ThebaudSea was a new vessel that had been in service for fifteen months at the time of the occurrence. The vessel was certified, crewed, equipped and operated in accordance with existing regulations for a vessel of her size, type and the trade in which she was engaged. The master's experience included command on various tugs and offshore vessels since 1978. The chief engineer had served on various vessels for approximately twenty-five years and the third engineer had approximately fifteen years of watch-keeping experience in the engine room. All crew members of the ThebaudSea had completed Marine Emergency Duties training. Main Generator Maintenance The No.4 main generator had 5737 running hours at the time of the occurrence. Maintenance records indicated that the generator had been inspected and maintained according to the manufacturer's recommendations. The last inspection was performed 232 hours prior to the occurrence and revealed no problems with the generator. Examination of the No.4 Main Generator Photo2. Typical generator a- Intact fuel fitting/connection b- Exhaust manifold/potential source of ignition The No.4 main generator was examined by the Transportation Safety Board of Canada (TSB) on the morning of 04February2001. The primary fuel oil filter housing runs the width of the generator and is located just forward of the generator and aft of the freshwater header tank. The secondary fuel oil filter housing runs half the breadth of the generator and is located directly above the primary fuel oil filter housing on the inboard side of the generator. The fuel oil selector cock was found to be in the MAIN RUN position, indicating the primary fuel oil filter was in use at the time of the occurrence. Directly aft of the primary and secondary fuel oil housings are the cylinder heads, a charge air after-cooler and the metal shielded exhaust manifolds. The two exhaust manifolds, with temperatures of about 1150F (620C), are within 60cm of the failed fuel fitting/connection. Photo3. Possible fuel sources a- Damaged fuel fitting/connection (primary source of fuel) b- Damaged fuel hose (secondary source of fuel) The area of the generator in way of the fuel oil filters, freshwater header tank and forward-most cylinder heads was charred and covered with a combination of soot and debris that had fallen through the overhead grating. An area of cleanburn was noted directly overhead of the fuel filters in way of distorted sections of open steel grating. There are also indications in the form of oily soot that fuel oil had flowed down the front of the generator. Inspection of sooting, charring and shadowing patterns on the generator indicate that the seat of the fire was located aft of the fresh water header tank on the generator, and extended aft toward the exhaust manifold located between the cylinder banks. Primary Fuel Oil Filter Inspection of the primary fuel oil filter revealed that a composite fuel oil pressure sensing line, which consisted of a hydraulic hose and copper tubing, had failed in way of the hydraulic hose. The two hydraulic hose termination fittings were found affixed to the primary fuel oil filter and the copper tubing respectively. The badly charred hydraulic hose was found disconnected from both fittings and lying on top of the generator. Secondary Fuel Oil Filter Inspection of the secondary fuel oil filter revealed a partial separation of the fuel oil outlet elbow from the end cover assembly. The separation was such that an O-ring, normally captured within the fuel oil filter end cover and completely hidden from view, was clearly visible. When the secondary fuel assembly was removed from the generator, extensive thread damage was noted on both the elbow and end cover assembly connections. Fuel Fitting/Connection Failure Photo4. Note extensive thread damage on the 90 elbow connector (D) and the secondary fuel oil filter end bell (E) As part of the investigation, the failed fuel fitting/connection and the damaged flexible fuel hose were sent to the TSB Engineering Branch for evaluation. A thorough examination and analysis of the items were carried out and Engineering Report LP16/2001 yielded the following conclusions. Separation of the 90 elbow connection resulted from extensive wear of the mating threads of the elbow and the internal threads of the fuel filter end bell fitting, probably initiated by a loss of torque or backing off of the jam nut assembly. The original looseness in the connection, provided by the combination of straight threads on the connector and slightly tapered threads in the end bell fitting, would have facilitated the relative motion of the threads driven by the normally imposed generator vibrations. Leakage past the degenerated threads of the connection would appear to have provided the source of fuel for the fire. The hoses used in the generator would appear to be of a satisfactory type and construction for use in pressurized fuel systems using marine fuel oil. The fuel hose, which was found separated after the fire, was believed to have failed well into the fire sequence. Alarm and Monitoring System The main and auxiliary machinery, as well as a fire detection system, are monitored by a data logging alarm and monitoring system (AMS). When a monitored parameter falls outside a pre-determined range, the alarm system detects the abnormality and enters an alarm state. This causes an audible and visual alarm to activate. Cancelling an alarm is a two-stage process that involves first silencing the alarm and then accepting it. Silencing the alarm only cancels the audible and visual alarms. To reset the alarm system to detect a subsequent alarm, it must be accepted. An examination of the AMS data logger printout revealed that the No.4 main generator had been plagued by numerous low fuel oil pressure alarms over the previous two months. After each alarm, the generator fuel oil pressure was visually checked to determine its authenticity. In each case, the fuel oil pressure was observed to be normal and the alarm to be false. To prevent re-occurring false alarms, it was common practice to silence the alarm, but not accept it. This action effectively left the fuel oil pressure monitoring function inactive. It was noted the No.4 main generator had suffered a low fuel oil pressure alarm which had been silenced, but not accepted/reset, approximately five and one-half hours prior to the occurrence. This resulted in the fuel oil pressure being unmonitored by the AMS at the time of the fire. The normal fuel oil pressure for the No.4 main generator is 4.0bar with the low fuel oil pressure alarm set at 2.0bar. The minimum rated capacity of the fuel oil booster pump is 1260litres per hour. At the time of the occurrence, the specific fuel consumption of the generator was estimated to be 310litres per hour. Emergency Fuel Oil Shut-Off System Photo5. Fuel oil shut-off station The vessel is equipped with a manually operated, hydraulically actuated quick-closing valve system. The actuating system is connected through tubing and a series of petcocks to quick-closing isolation valves in the port and starboard engine rooms. The quick-closing valves, connected to the port and starboard day tanks, are used to quickly isolate all fuel flow from the selected tank in the event of an emergency. To prevent inadvertent operation of the quick-closing valves, the petcocks are normally left in the open position. This prevents any pressure build up in the signal lines as a result of temperature rise, by allowing the oil in the lines to expand and bleed back to the small header tank. To activate/close a valve, the appropriate petcock is left open and all remaining petcocks are closed. A small hydraulic hand pump is operated and produces pressure in the signal line, which activates a small piston mounted on top of the respective valve. This in turn trips/closes the valve. Once tripped, the only way to open the valve is to go to the valve and manually reset it. Dynamic Positioning System The ThebaudSea is equipped with a dual redundant dynamic positioning system with a Det Norske Veritas DYNPOS AUTR designation. To meet an AUTR designation, a vessel must have an automatic position keeping system with redundancy in technical design. Some of the advantages of the dual redundant system are as follows. The system is designed to avoid a total system failure in the event of a single failure. If a system component fails, the other components will not be affected. The working component of the system allows for corrective action to be taken by detecting a failure. If the on-line computer in the system fails, an automatic switch-over to the stand-by computer will occur.